[Plugin: Members Only] not working with pdf pages

Hi, I understood that anything contained inside the wp-content folder had to be unaccessible to not logged users but actually it doesn’t work that way. All pdf files are perfectly viewable to non-members as far as they paste the correct link in the browser. I also protected all files from downloads but pdf are considered pages by most part of browsers and therefor they are still showing up. Any way around this?

thx

http://wordpress.org/extend/plugins/members-only/